Nine seconds after the Penguins prevented Washington's potent power play from scoring on a double-minor, Niskanen scored the winning goal to give the Penguins their 10th consecutive victory, 2-1 against the Capitals on Tuesday night.

Niskanen's wrist shot with 8:02 to play in regulation came off a 3-on-2 rush with assists from Matt Cooke and Sidney Crosby, as he beat Washington goalie Braden Holtby high to the glove side. That ramped up the roar from a crowd that moments earlier was in a frenzy when Pittsburgh cleared its zone to end sustained Capitals pressure after Marc-Andre Fleury made consecutive saves.

"The penalty kill did an amazing job of stepping up to the challenge, and we created a lot of energy and some momentum from that," Niskanen said. "You could feel the crowd getting into it, and we were able to go out on a rush there and finish and get the game-winner."

Crosby also assisted on Martin's second-period goal for the Penguins, who are on the fifth winning streak of at least 10 games in franchise history.

Pittsburgh, which has also won eight in a row at home, has the second-longest winning streak in the National Hockey League this season. They can tie the Chicago Blackhawks' 11-game run with a win Friday night when they visit the New York Islanders.

Alex Ovechkin scored for the third time in four games for Washington, which has lost five of seven and is seeing its hopes of a sixth consecutive playoff berth slipping.

The Penguins (23-8-0) have no such worries; they lead the Eastern Conference standings and have opened up a 14-point lead over the New Jersey Devils and New York Rangers in the Atlantic Division.

Before the game, Crosby was marveling at the way it's been a different hero or unit deserving of the credit every night of the winning streak. Against the Capitals, it was the much-maligned penalty killers who played a pivotal role.

Pittsburgh entered Tuesday with the League's 22nd-ranked penalty kill despite not allowing a power-play goal in its previous three games.

Washington's four-minute power play began with 12:11 left in regulation when Cooke was called for boarding and unsportsmanlike conduct.

"That power play was going to be the game," Washington forward Eric Fehr said. "I think everybody knew it."

That figured to benefit the Capitals, who entered the game with the NHL's third-ranked power play and had scored their only goal with the extra man in the second period. But instead of using this opportunity to snap the winning streak of what many Washington players called their biggest rival, the Penguins seized the momentum with a strong penalty kill.

"Four minutes, and we have only two shots on net," Ovechkin said. "It's awful. It killed us."

The Penguins played their first full game this season without either Evgeni Malkin or Kris Letang. The NHL's reigning MVP and its leading scorer among defenseman, respectively, are out due to injury.

Letang left Sunday's win against the Boston Bruins with a lower-body ailment while Malkin missed his sixth consecutive game because of an upper-body injury. Malkin participated in the morning skate and expressed hope he could play Friday on Long Island.

Fleury made 28 saves to win his sixth straight start for the Penguins, who have allowed just six goals in their past six games.

"We're obviously missing big parts of our hockey team," Crosby said. "So we're keeping it simple and trying to find ways to have success and hopefully waiting for these guys to get back."

Ovechkin opened the scoring 8:14 into the second period during a power play when he fired a loose puck that had squirted to him in the left circle past Fleury for his 12th of the season. Martin tied it 2:53 later with a power-play goal of his own -- he stepped into a puck set up for him by Crosby in the high slot and slapped it high past Holtby's glove for his sixth of the season.

Washington was playing the first of four games in six days on the road, its longest trip of the season. Ovechkin and other Capitals made no secret of the make-or-break aspect of this stretch. Washington remained seven points out of a playoff spot.

The Capitals welcomed back versatile forward Brooks Laich, who made his season debut after sustaining a groin injury before the season began. He was quickly promoted from the fourth line, played on the penalty-killing and power-play units and had one shot and three hits in 12:51 of ice time.

Dmitry Orlov also made his season debut for Washington, the latest defenseman to play for a team that has been hit hard by injuries on the blue line. Orlov had one blocked shot in 11:58 and was on the ice for 1:07 of the failed power play that decided the game.

Even before the Penguins scored, their partisan crowd roared. Bylsma and Martin said it was the loudest they'd heard the three-year-old building this season.

"They were more excited for the PK than for my goal, I think," Niskanen said with a chuckle. "That's OK though."

The Penguins' metamorphosis during the midst their winning streak is striking. They scored at least four goals during each of the first five victories -- but have not scored more than three in a game since.

Defensively, they averaged more than four goals against per game in the first four wins of the streak -- but only 1.00 per contest in the six that have followed.